This invention relates to a method of manufacturing electrical windings used for rotating electric machinery for rail and road vehicles, etc. More particularly, the invention pertains to an electrical winding manufacturing method which can be effectively applied to the manufacture of various types of electrical windings including the wires differing in shape, size and function while enabling the respective windings to perform the required functions.
Various methods have been employed for manufacturing the electrical windings. For example, in the case of field equipment for DC motor for rail vehicles, as illustrated in FIG. 2 of the accompanying drawings, a conductor 1 is wound several turns and a high-viscosity compound resin 2 is applied to the angular portion a on the inside to smoothen the surface of the conductor 1. Then a mica tape or a film is wound and, after providing an insulating layer 3, an impregnating low-viscosity resin is impregnated and hardened to form a field coil 4. Thereafter, the field coil 4 is inserted into a core 5 and a bonding high-viscosity resin 6 is cast into the space and hardened, thereby forming a field equipment 7. The techniques relating to this type of manufacturing method are disclosed in, for instance, Japanese Patent Publication No. 57-55013 (1982).
In another conventional method, as illustrated in FIG. 3, a conductor 1 is wound several turns; a non-woven cloth 8 is stuffed into the angular portion a on the inside; a mica tape or a film is wound; an insulating layer 3 is provided; the assembly is inserted into a core 5 through the medium of a non-woven cloth 9; and then an impregnating low-viscosity resin is integrally impregnated and hardened to form a field equipment 7. The techniques relating to this type of method are shown in, for instance, Japanese Utility Model Application Laid-Open No. 61-133436 (1986).
Recently, with an increasing tendency toward speed-up of vehicles, request has become stronger for enlargement of capacity of vehicle motors and reduction of size and weight of the parts. Strong request has also been voiced for the improvement of reliability of the windings for electric machinery. As for the method of manufacturing such electrical windings, of the two types of method mentioned above, the latter type of method in which an impregnating low-viscosity resin is integrally impregnated and hardened to form a uniform insulating layer and which is more suited for meeting said requirements has gained ground.
On the other hand, field equipment for DC motor for vehicles, as illustrated in FIG. 1 and as generally known, has a main pole coil 10 and an interpole coil as well, the latter being smaller than the main pole coil 10 and adapted for preventing movement of the neutral point caused by inconstant rotational speed of the motor and thereby bettering commutation. It is to be also noted that recently, in order to keep pace with speed-up of vehicles, remarkable strides have been made for the enlargement of capacity, speed-up and extension of the scope of speed adjustment of vehicle motor, and the influence of the distortion of reflux distribution in the main pole due to armature reaction has become innegligible. In the recent field equipments, therefore, a slot is provided in the core portion of the main pole and the compensating coils 30 having the insulating layers are placed therein to counteract the armature magnetomotive force.
Thus, the recent models of field equipment for DC motor for vehicles are usually provided with the electrical windings having different shapes and functions.
As mentioned above, the recent models of field equipment are mostly of a structure having plural electrical windings differing in function from each other, and as for their manufacturing method, a method comprising integral impregnation and hardening of an impregnating low-viscosity resin is most popular. However, when it is tried to manufacture a field equipment by simply combining these two concepts, there arise the problems such as mentioned below.
(1) The electrical windings used for field equipment differ in size (heat capacity) from each other, so that even if an impregnating low-viscosity resin is integrally impregnated and hardened, the rise of temperature in heat hardening differs and therefore the time required for the impregnated resin to harden (gel time) varies from one winding to the other, hence a possibility that the insulating layers formed may be non-uniform in properties.
(2) The shape of the electrical windings differs according to the type like main pole coil, interpole coil and compensating coil. For example, compensating coil is small in sectional area and long in distance between core end and coil end (hereinafter referred to as xe2x80x9cprojection lengthxe2x80x9d). Main pole coil is large in sectional area and short in projection length. The properties required of the insulating layer differ from one winding to the other though withstand voltage is same, so that it is hardly possible to satisfy all the property requirements with a single insulating specification. For example, compensating coil is required to have a high mechanical strength as the projection length is large. On the other hand, main pole coil, because of its large sectional area, is high in rate of heat dissipation from the conductor, so that this type of winding is required to have a uniform heat conductivity and to keep free of delaminating layer such as air layer which hinders heat transfer between the insulating layers.
In order to solve the problem, Japanese Patent Application laid-Open No. 3-285540 discloses a method of manufacturing electrical windings comprising plural steps, wherein same materials are used for impregnating resins, but the sort of additives and/or hardening temperature is varied to apply impregnating resins to respective coils. However, such a method is complicated because the plural steps are necessary.
The object of the present invention is to provide a method of producing windings for electric machinery, according to which it is possible to produce, with high efficiency, the electrical windings differing in function and capable of performing the functions required of them respectively.
The above object of the invention can be accomplished by forming the insulating layers suitable for the respective types of electrical windings, that is, the windings differing in function, in the step of applying insulation on the windings formed by winding a conductor, and impregnating a single impregnating insulating resin in the different types of windings and hardening the resin in the step of setting the insulated windings in a core.
The above object of this invention can be also achieved by changing the properties of the insulating layers depending on the respective types of windings by changing the insulating material forming the insulating layers in the step of applying insulation, or by changing the properties of the insulating layers depending on the respective types of windings by changing the way of addition of the hardening accelerator which is reacted with the insulating resin added to the insulating material forming the insulating layers and determines the properties of said insulating resin in said step of applying insulation, or by changing the properties of the insulating layers depending on the respective types of windings by changing the kind of the hardening accelerator which is reacted with the insulating resin added to the insulating material forming the insulating layers and determines the properties of said resin in said step of applying insulation.
Said object of this invention can be also attained by changing the properties of the insulating layers depending on the respective types of windings by using a mica tape supported on a film for the insulating layers in the case of the windings which are small in heat capacity in heat drying of the impregnating resin because of small sectional area of said windings, or by using a mica film with glass cloth for the insulating layers in the case of the windings which are large in heat capacity in heat drying of the impregnating resin because of large sectional are a of said windings, in said step of applying insulation.
Moreover, the method of the present invention is also excellent in simplicity as compared with conventional ones because application of the impregnating resins can be carried out in a single step in the present invention.